for the link to the heat disks. You might also be able to find them at PetsMart or some other pet store.
I use a birdbath heater to keep the water from freezing. I use a lasrge flat birdbath, placed on the ground rather than on a post, and have the heater in the water. I've used this for years..it works great. But, for Dumac and others who don't have access to electricity, I don't have a clue how to help.